Wrinkle smootheners are required for automated bending of tubes having small wall thicknesses and at the same time small bending radiuses, said smootheners preceding the bending mandrel when viewed in the feeding direction of the tube. If the tube is clamped, on the one hand, between the clamping device and the bending mandrel and is, moreover, received between the two sliding jaws of the wrinkle smoothener, it is not possible for the tube to yield in an uncontrolled manner on the internal radius side during the bending operation. This makes it possible to also bend thin-walled tubes having a small bending radius. Therefore, wrinkle smootheners are employed in tube bending so as to improve the bending result. However, the use of wrinkle smootheners is problematic in bending machines in which the bending head is stationary. This is because, in order to generate both left-hand and right-hand bends with such machines, it has to be possible to place the tube in contact on opposite sides of the central axis of the bending mandrel. However, if the bending process requires a wrinkle smoothener in both bending directions, there is the problem in these known machines that the wrinkle smoothener, since it is permanently attached to the machine body, has to be manually shifted and newly aligned when changing the bending direction. This means that an operator has to be present at the bending machine at all times, and therefore it has been attempted to limit the use of a wrinkle smoothener to only one bending direction. However, such limitations almost always turn out to be of great disadvantage to users of the bending machines.
A machine comprising such a wrinkle smoothener is known from DE 696 24 723 T2, wherein, for operation, the sliding jaws of the wrinkle smoothener are connected to each other and biased against each other by locking elements, which are mounted, longitudinally spaced apart, to the outer periphery of the sliding jaws.
In the arrangement described in U.S. Pat. No. 5,222,552 a wrinkle smoothener is provided with only one sliding jaw, however, which can only be made to unilaterally contact the workpiece on the side of the bending mandrel and is also securely mounted to the machine frame, but can be laterally folded away from the workpiece or onto it.
The wrinkle smoothener of DE 201 18 444 U1 is also securely attached to the machine frame.
Tube bending apparatus of the above-mentioned type has been known in the market for a short time, said apparatus being adapted for both right-hand bending and left-hand bending of a workpiece about a bending mandrel and employing a wrinkle smoothener which can be used in both bending directions. The wrinkle smoothener comprises two sliding jaws, one of which is displaceable towards the other. A sliding jaw which is laterally arranged on the bending tool—viewed relative to the workpiece—is mounted to a support which is mounted to the bending head such that, although it is concentrically rotatable relative to the bending mandrel, it is not movable towards the latter.
A specific problem common to all the aforementioned wrinkle smootheners is that, if the wrinkle smoothener or its forming groove is not aligned absolutely precisely, there may be a risk of edges deflecting, so that precise alignment of the wrinkle smoothener is of particular importance also with respect to its overall effectiveness. The operations to be carried out for this purpose, which always have to be effected anew, in particular also when refitting a wrinkle smoothener, have to be carried out with great precision and are time-consuming.